Spring mechanism for vibrating rectifiers



A. L. ATHERTON.

SPRING mscn mlsm FOR VIBRATING RECTIFIERS.

APPLICATION FILED DEC-29, I9I5- Patented Oct. 12, 1920.

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INVENTOR Alfred I ATherTon.

I ATTORNEY Strain.

WITNESSES: 0?; c5 I W 25 UNITED STATES PATENT OFFICE.

ALFRED L. ATHERTON, or WILKINSBURG. PENNSYLVANIA, ASSIGNOR 'ro WESTING- HOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYL.

VANIA.

SPRING MECHANISM FOR VIBRATIN G RECTIFIERS.

Specification of Letters Patent.

Patented Oct. 12, 1920.

Application filed December 29, 1915. Serial No. 69,173.

'1 0 all whom it may concern:

Be it known that I, ALFRED L. ATHERTON, a citizen of the United States, and a resident of Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Spring Mechanism for Vibrating Rectifiers, of which the following is a specificaton.

My invention relates to spring mechanism for vibrating rectifiers, and it has for its object to provide apparatus of the type. described that shall permit successful operation. ofa rectifier with an alternating-current source of variable frequency and w th the consumption of but little energy 1n dr1ving the rectifier itself.

In the accompanying drawing, Figure l is a diagrammatic view of a vibrat1ng rect1- fier of the type shown and claimed in the U. S. Patent No. 1,184,233, issued to the \Vestinghouse Electric & Manufacturlng Company on an application filed by Edgar Giglio and embodying a preferred form of my invention; Figs. 2,. 3, 4 and are fragmentary views showing modifications of the spring mechanism employed RIF 1g. 1, and embodying modifications of my invention; and Fig. 6 is a diagram illustratlng the changing ratio of stress to strain in the spring mechanism shown in Figs. 1 to 5,'inelusive.

In the operation-of mechanical rectlfiers of the type wherein a contact-carrying armature is driven in synchronism with the frequency of the alternating current to be rectified and is employed to perlodleally make and break current-carrying contacts for supplying direct current, it is desirable that said armature be vibrated at a forced rate rather than atits natural rate, as fully pointed out in the U. S. Patent No. 1,192,741 issued July 25, 1916 to the lVestinghouse Electric & Manufacturing Company on an application filed by Quincy A. Brackett. Too great a divergence between said natural and said forced vibratory rates necessitates the expenditure of an exorbitant amount of energy in driving the rectifier itself and it 1s therefore desirable that said forced rate closely approximate to the natural rate. A change in the frequency of the alternatlng-current source disturbs the desired adjustment and it is the purpose of this invention to provlde means whereby a rise in the frequency of the alternating-current supply, with an attendant lncrease in the forced frequency of vibratlon, causes a corresponding increase in the natural frequency of the armature and vice versa. To achieve this end, I avail myself of the phenomena that an approach of the forced and natural frequencies increases the amplitude of vibration and divergence decreases the amplitude of vibration, said changes in amplitude being employed to alter the spring-controlling forces in the armature and hence to alter the natural vibratory period thereof.

Referring to the drawing for a more detailed understanding of my invention, I show a source of alternating-current at 7 in Fig. 1, said source preferably comprising the secondary winding of a transformer the primary winding 8 of which is connected to suitable mains. Current is supplied from the right hand half of the winding 7 to suitable driving magnets 9 and 10 through a phase and current-adjusting device 11. A polarized vibratory armature 12 is mounted vwith its ends adjacent, respectively, to the magnets 9 and 10 and carries contact members 13 and 141 arranged to make and break contact, respectively, with fixed contact members 15 and 16 for the rectification of current, all as is well known and understood in the art. Spring members 17 and 18 are attached to the ends of the armature 12 and bear upon fixed stop members 19 and 20. Pins 21 and 22 are mounted upon the armature 12 and are adapted to make contact with, and shorten the effective length of, the springs 17 and 18 when the amplitude of vibration of the armature 12 exceeds a certain predetermined amount.

Having thus described the structure of a rectifier embodying my invention, the operation is as follows: Assuming that the source 7 supplies alternating current at a frequency of, for example, 25 cycles, the springs 17 and 18 and stop members 19 and 20 are so adjusted that the natural frequency of vibration of the armature 12 is, for example, thirty complete vibrations per second. The alternating-current energization of the driving magnets 9 and 10 forces the armature to vibrate in synchronism with the frequency of the alternating-current source that is to say, the armature assumes a forced vibration of twenty-five complete move ments per second. Under these conditions, the pin members 21 and 22 do not make contact with the springs 17 and 18. If now, the frequency of the supply rises to twenty-eight cycles per second, for example, the close approach of the resultant forced frequency of vibration of the armature 12 to its natural frequency produces a marked increase in the amplitude of vibration thereof, and the pins 21 and 22 thereforemake contact with the springs 17 and 18, respectively, during periods of great displacement. of the armature 12. -The impact of the pin 21 upon the spring 17 renders the portion of said spring between the point of contact and the point of attachment to the armature 12 substantially inactive, and the remaining portion of the spring is stiffer than was the entire spring; that is to say, it'requires the application of a greater force to produce a given deflection, or, in the terms of mechanics, there is a reater ratio of stress to strain. As a result, a greater spring-controlling force is obtained and the natural vibratory frequency of the armature 12 is raised, for example, to thirty-two cycles per second, thus maintaining substantially the desired difference between the forced and the natural frequency;

The springs 17 and 18 may or may not leave the stops'19 and 20 when'the vibratory member is moving at maximum amplitude. However, if, for example, the spring 17 leaves the stop 19, at a given instant, thus tending to decrease the controlling force, the simultaneous operation of the pin 22 upon the spring 18 causes such an increase 'in the controlling force as to overcompensate for the absence of activity on the part of the spring 17. Thus there is a net increase in the controlling force with an increase of amplitude in the movement of the armature 12.

Referring to Fig. 6, wherein the ordinates represent stress and the abscissae represent strain, the line 2324 is the stress-strain diagram of the springs 17 and 18 when operating throughout their entire lengths, the line 2526 is the stress-strain diagram of the active tip of a spring when the pins 21 and 22 are operative, and the resultant effective stress-strain diagram is shown by the line 23-26. The greater steepness of the line 23-26, as compared with the line 2324, is a measure of the increase in the ratio of stress to strain and, therefore, of the increase in the controlling force and in the natural vibratory rate in the armature 1'2.

In the form of my invention shown in Fig. 2, the armature 12 is provided with a spring member 27 arranged to make contact with a stop member 19 and provided with an upwardly and inwardly curved tip portion 28 which makes contact with the armature 12 when the amplitude of vibration exceeds a predetermined amount, producing a similar action to that of the structurev shown in Fig. 1.

In the form of my invention shown in Fig. 3, the armature 12 is provided with a spring member 17 cooperating with a stop member 19, as is Fig. 1, and is also provided with a short, stiff, auxiliary spring 29 which comes into action only during vibrations of considerable magnitude.

The form of my invention shown in Fig. 4 is substantially the same as that shown in Fig. 3 except that the auxiliary spring 29 cooperates with an auxiliary stop member 30 rather than with the main stop member 19.

When operating a rectifier at higher commercial frequencies, such, for example, as sixty cycles, it is desirable to 30 design the structure that the natural period of vibration of the armature is below, rather than above, the forced vibrating'rate. Assuming, therefore, that a rectifier is operating upon sixty cycle current and that the natural rate of vibrationof the armature thereof is fifty-five cycles per second, a drop in the operating frequency to fifty-eight cycles per second, for example, would necessitate a weal ening in the control springs by the action of the increased amplitude produced by the approach of the forced to the natural rate of vibration and a consequent lowering in the natural rate to fifty-four cycles per second. This result may be produced by employing the structure shown in Fig. 5 wherein the armature 12, provided with springs 17 and 18 coactin respectively with stop members 19 and 20, is so adjusted that, with small amplitudes of vibration, each spring makes contact with its respective stop member throughoutthe entire movement but wherein, at greater amplitudes, the spring members 17 and 18 alternately leave their respective stop members to momentarily impose the entire spring control upon the other spring. As a result, at small amplitudes, both springs being operative at all times, there is a relatively high stressstrain ratio present and, consequently, a high natural rate of vibration, whereas, at greater amplitudes with but one spring active during portions of each vibration, the stress-strain ratio is lowered and, consequently, the natural rate of vibration of the armature is lowered.

Referring again to Fig. 6', the line 23-2 represents the stress-strain ratio of the structure of Fig; 5 when the springs 17 and 18 are both operative throughout the entire cycle, and the line 25-31 represents the stress-strain ratio of either of the springs 17 and 18 when operating, at times, alone. The resultant stress strain ratio for the entire cycle may be represented by the line 23-31, and the steepness of the line 23-31, as compared with the line 2324, is a measure of the drop in the natural frequency brought about by the spring structure set forth.

While I have shown my invention in its preferred form, it will be obvious to those skilled in the art that it is susceptible of various minor changes and modifications Without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or are specifically set forth in the appended claims,

I claim as my invention:

1. In a vibratory rectifier, the combina tion with a pivoted armature, of resilient means associated therewith forbiasing the same to a neutral position and for impartmg a natural frequency of vibration thereto, variable-frequency vibrating means therefor, and means for automatically altering said natural,frequency of vibration in accordance with changes in said variable oper ating frequency.

In a vibratory rectifier, the combination with a pivoted armature, of resilient means associated therewith for biasing the same to a neutral position and for imparting a natural frequency of vibration thereto, variable-frequency vibrating means therefor, and auxlliary resilient means for automatically altering said natural frequency of vibration in accordance with changes in said variable operating frequenc 3. n a vibratory rectifier, the combination with a pivoted armature, of resilient means associated therewith for biasing the same to a neutral position and for imparting a natural frequency of vibration thereto, variable-frequency vibrating means for operating said armature at other than its natural frequency, and mcans for automatically altering said natural frequency of vibration with changes in said operating frequency, whereby a difference is maintained between said natural frequency and said operating frequency.

4. In a vibratory rectifier, the combination with a pivoted armature, of resilient means associated therewith for biasing the same to a neutral position and for imparting a natural frequency of vibration thereto.

variable-frequency vibrating means operating said armature at other than its natural frequency, and auxiliary resilient means for altering said natural frequency with changes in said operating frequency, whereby a difference is maintained between said natural frequency and said operating frequency.

5. In a vibratory rectifier, the combination with a pivoted armature, of resilient means associated therewith for biasing the same to a neutral position and for imparting a natural frequency of vibration thereto, variable-frequency vibrating means operating said armature at other than its natural frequency, and auxiliary resilient means for altering said natural frequency with changes in said operating frequency, whereby a substantially constant difference is maintained between said natural frequency and said operating frequency.

6. In a mechanical rectifier, the combination with a vibratory, contact-carrying armature arranged to control the connec tions between a direct-current load and an alternating-current source subject to changes in frequency, of means for forcing said armature to vibrate at the frequency of said source, and means for causing the natural frequency of vibration thereof to differ slightly from said forced frequency at all times.

7 In mechanical rectifying apparatus for alternating currents of variable frequency, the combination with means for causing a vibratory, contact-carrying armature to as sume a forced vibration in synchronism with said frequency, of means for causing the natural vibratory frequency of said armature to differ but little from said forced I frequency at all times.

8. In mechanical rectifying apparatus for alternating currents of variable frequency, the combination with a vibratory contactcarrying armature, of control springs there-- for, operating means for establishing forced vibration thereof in synchronism with said source, and means operative by the increase in amplitude of vibrations attendant upon an approach of said forced frequency to the natural frequency of said armature for increasing the difference therebetween and operative by the decrease'in amplitude of vibrations attendant upon a departure of said forced frequency from the natural frequency of vibration of said armature to decrease the difference therebetween.

9. In a mechanical rectifier, the combination with a vibratory contact-carrying armature, of resilient controlling means associated therewith, and vibrating means therefor, the controlling force exerted by said resilient means varying with a change in the amplitude of vibrations of said armature at other than a direct ratio.

10. In a mechanical rectifier, the combination with a vibratory contact-carrying armature. of resilient controlling means associated therewith. and vibrating means therefor. the controlling force exerted by said resilient means varying with a change in the amplitude of vibration at a greater rate than the rate of'change in said amplitude.

In testimony whereof, I have hereunto subscribed my name this 22nd day of Dec ALFRED L, ATHERTON. 

